A Case for Global Soil Restoration

David R. Montgomery Department of Earth &

Space Sciences University of Washington

Soil is a Strategic Resource

Global soil degradation is an under appreciated crisis

Over the last 40 years soil erosion and degradation has caused farmers to abandon about 430 million ha of arable land, an area equivalent to about one-third of all present cropland.

The estimated rate of world soil erosion in excess of new soil production is 23 billion tons/yr, or about 0.7% loss of the world's soil inventory each year.

Pimental et al., 1992

Natural Disasters

No real mystery that some of the key controls on the longevity of human societies are …

Politics, War, and Social Evolution

Climate Change

But what about soil? The fundamental condition for sustaining a civilization is sustaining the soil and its fertility.

Mesopotamia Minoans Greece

Rome

Indus Angkor Watt

Olmec Maya Inca

Soil erosion resulting from deforestation has been proposed to explain the demise of civilizations around the world.

Recent archaeological studies showed that soil erosion played a role in the demise of ancient civilizations of Neolithic Europe, Classical Greece, Rome, the Southern United States, and Central America.

Erosion

Weathering

Invention of the plow fundamentally altered the balance between soil production and soil erosion, dramatically increasing soil erosion…

USDA (1979)

Palouse, Washington

1961

In researching the book, I began compiling additional data on both contemporary and long-term (geological) erosion rates—and agricultural erosion rates in particular…

1402 measurements of agricultural and geological erosion rates

Did not include USLE-based model studies

USDA soil loss tolerance values range from 0.4 to 1 mm/yr

Conventionally plowed farms erode like alpine topography Conventional agriculture unsustainable in soil-mantled landscapes

Probability distributions for geological erosion rates, erosion under native vegetation, and by no-till agriculture are all comparable.

Agricultural soil loss is not because humanity farms but arises from how we farm — from using the plow.

Measurement type median mean

(sample size) (mm/yr) (mm/yr)

Conventional (448) 1.537 3.939

Conservation (No-till) (47) 0.082 0.124

Native Vegetation (65) 0.013 0.053

Soil Production (188) 0.017 0.036

Geological (925) 0.029 0.173

Erosion Rates

Global erosion rates have increased by more than an order of magnitude due to human activity…

Average erosion rate for last 500 million years = 1 inch / 1400 yrs

Average rate of soil production at present = 1 inch / 500 yrs

Average rate of soil erosion at present = 1 inch / 60 yrs

(Wilkinson, 2005)

Net soil loss of ≈ 1 mm/yr implies that erosion of a typical 0.5 - 1 m thick hillslope soil could occur in roughly 500 to 1000 years; approximately the lifespan of most major civilizations outside of major river floodplains…

Here in a nutshell, so to speak, we have the underlying hazard of civilization. By clearing and cultivating sloping lands—for most of our lands are more or less sloping—we expose soils to accelerated erosion by water or by wind…. In doing this we enter upon a regime of self-destructive agriculture.

- [Lowdermilk, 1953, p. 26]

National Archives: 114 SC 5089

A nation that destroys its soils, destroys itself. – President Franklin D. Roosevelt, Feb. 26, 1937.

Is Soil Restoration Possible?

Can we reverse the historical pattern?

Rebuilding Soil

We can build soil surprisingly fast — faster than nature does…

It takes organic matter, effort (labor), and biological assistance (microbes).

Fertile carbon-rich soils built by anthropogenic activity in the Amazon and reclaimed sea beds in northern Europe.

Terra Preta

Plaggen

Why bother restoring soils? To Address Global Challenges of the 21st Century

Feeding a Post-Oil World

Carbon Sequestration (Climate Change)

Public Health / City Livability

Biodiveristy / Environmental Degradation

Restoring soil could be the foundation for partial solutions to all of these problems…

Peak Oil A Question of When

20th Century Strategy Intensification of Fertilizer Use

Can we really maintain this strategy in the long run as oil supplies dwindle and prices rise dramatically later this century?

Feeding A Growing Population …

… A Growing Problem

Amount of arable land per person is declining and is projected to fall to ≈ 0.1 ha per capita by 2050.

How will we feed a post-oil world without cheap fertilizer-intensive agriculture?

A Greener Revolution?

Crop yields from no-till and organic agriculture can compete with those from conventional agriculture, and over time exceed them on degraded land …

No matter how one looks at it restoring native soil fertility would be really useful for sustaining agriculture in a post-oil (and post-cheap fertilizer) world.

Soil and Climate Change

By the late 20th Century, a third of carbon added to atmosphere since the Industrial Revolution came from degraded soil organic matter.

We can put that much (and more) back in the ground through:

(1)  increasing soil organic matter

(2)  biochar

Lal (2004) estimated that changes in agricultural practices could sequester 0.4 to 1.2 Gt C per year, enough to offset 5-15% of global fossil fuel emissions.

Amundson (2001) noted that cultivation and deforestation releases >4 Gt C per year, equivalent to more than half global fossil fuel emissions.

Global Agriculture, Land Use and Carbon Emissions

Biochar:

Global soil C≈1500 Gt Global atmospheric C≈760 Gt

Average residence time for SOC globally is less than 2 decades.

Biomass decay ≈60 Gt/yr Fossil fuel emissions ≈7 Gt/yr

Capture of ≈10% of global annual biomass decay as biochar would offset global fossil fuel emissions.

“The significant problems we face cannot be solved at the same level of thinking we were at when we created them.”

Time For A New View of Soil?

Soil as a mystery, fertility to be personified, deified and revered.

Soil as a means to a living, land to be worked.

Soil as a decipherable mystery, something to be studied and understood.

We know more about the movement of celestial bodies than about the soil underfoot.

- Leonardo da Vinci

Soil as a chemical reservoir, a medium to be fertilized as needed.

Soil as an industrial commodity to be used (and used up).

Soil as an ecosystem to be understood and worked with...

Soil Ecology — the Future of Agriculture?

Can we harness the insights of soil ecology to restructure agricultural technology to feed the world based on ecological processes and nutrient cycling?

This is not really a question of low tech organic versus GMO & agro-tech…

Question is how to apply an understanding of soil ecology to the applied problem of increasing — and sustaining — crop yields in a post-oil environment.

Key Questions …

How best to get organic matter back into the soil?

How much, how fast?

How to use soil ecology (microbial) processes to build soil fertility?

How do we better address linkages between soil health and human health?

Can we rebuild soils in cities?

Soil, Cities, and Public Health

As of 2009, more than half of humanity lives in cities.

Restoring urban soils can improve the quality of the built environment and thereby people’s health through:

• Green space/Urban nature • Physical Activity • Direct access to Fresh Food

Healthy soil is the foundation upon which human health and environmental health is built.

It all starts with the ground beneath our feet.

Healthy Soil: No Silver Bullet, But A Secret Weapon?

Restoring soils can help address:

• Feeding the World

• Climate change

• Public health (physical, mental, and

social)

First and foremost soil restoration means …

… we have to stop treating soil like dirt!

Thank You